Sheet stacking apparatus for a duplicating machine or the like

ABSTRACT

The duplicating machine includes an electrostatic copying unit, a conversion unit for converting each electrostatic copy to form a master sheet, and a duplicating unit for making a number of copies by direct contact between each master and receiving sheets. The stacking apparatus is mounted between the conversion unit and the duplicating unit and is adapted to stack masters in inclined relationship with a portion of the upper surface of each successive master in coextensive contact with a corresponding portion of the lower surface of the immediately preceding master. The stacking apparatus includes an inclined planar support with lifting means in the form of driven belts for engaging the underside of the trailing portion of each master. A control system permits the duplicating machine to operate in a continuous and fully automatic manner.

United.States Patent [191 Ziebka et al.

[ Jan. 15, 1974 SHEET STACKING APPARATUS FOR A DUPLICATING MACHINE OR THE LIKE [75] Inventors: Bernard M. Ziebka, Morton Grove;

Paul A. Tamburrino, Hoffman Estates, both of I11.

[73] Assignee: A. B. Dick Company, Niles, Ill.

[22] Filed: June 6, 1972 [21] Appl. No.: 260,110

[56] References Cited UNITED STATES PATENTS 2,082,240 6/1937 Belluche et al. 271/46 Primary ExaminerRichard E. Aegerter Assistant Exarrriaer-larnesjll lvliller ll tt bFr i ey lVlcDougall, Hersh & Scott [57] ABSTRACT The duplicating machine includes an electrostatic copying unit, a conversion unit for converting each electrostatic copy to form a master sheet, and a duplicating unit for making a number of copies by direct contact between each master and receiving sheets. The stacking apparatus is mounted between the conversion unit and the duplicating unit and is adapted to stack masters in inclined relationship with a portion of the upper surface of each successive master in coextensive contact with a corresponding portion of the lower surface of the immediately preceding master. The stacking apparatus includes an inclined planar support with lifting means in the form of driven belts for engaging the underside of the trailing portion of each master. A control system permits the duplicating machine to operate in a continuous and fully automatic manner.

10 Claims, 9 Drawing Figures PATENTEB JAN 51974 SHEET 3 BF 5 Pmmsmm w 3.785.639

FIG, 5

' If Mull." 3

SHEET STACKING APPARATUS FOR A DUPLICATING MACHINE OR THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to apparatus for stacking sheet material. More particularly, the present invention relates to a sheet stacking apparatus for mounting between first and second sheet feeding means, wherein the second sheet feeding means is adapted to receive the sheets one at a time from the first sheet feeding means and wherein the sheets are fed through the first sheet feedin means at a rate greater than the rate they are fed through the second sheet feeding means.

The present invention has particular, although not exclusive, applicability in a duplicating machine which includes a copying unit for making one or more electrostatic copies from a sheet of original material, a conversion unit or etcher for converting each electrostatic copy to a hydrophilic condition so that it may perform as a lithographic master sheet, and a duplicating unit operating in accordance with the well-known offset lithographic duplicating process to print copies mechanically by contact between a blanket cylinder and a receiving sheet. In such a machine, the elestrostatic copying unit and the conversion unit are capable of making master sheets faster than the duplicating unit is capable of completing a cycle involving the selected number of duplicate sheets.

2. The Prior Art Reference is made to Carper et al US. Pat. No. 3,426,678 which discloses a duplicating machine of the type generally referred to hereinabove. The machine shown in this patent has no means for storing or stacking the masters prior to the time they are ready to be used by the duplicating unit. According to the machine shown in the Carper et al, patentm each master is made only at a time when the duplicating unit is ready to receive the master.

Such a prior art machine does not permit utilizing the full capabilities of the electrostatic copying unit and the conversion unit which are capable of making lithographic masters at a rate much greater than the rate at which the duplicating unit is capable of receiving such masters. Further, since the electrostatic copies according to this prior art machine cannot be made rapidly, the original material from which such copies are made must be maintained at or nearby the electrostatic copying machine for substantial time periods which is disadvantageous in many situations. Still further, it is somewhat difficult to provide an automatic and continuous control system for such a machine as full advantage cannot be taken of the feature of the electrostatic unit which provides for the rapid and successive making of electrostatic masters from respective originals.

SUMMARY AND OBJECTS OF THE INVENTION The present invention relates to an apparatus for stacking successive sheets one under the other in an inclined manner, such apparatus having particular, although not exclusive, application in a duplicating machine of the type described and such apparatus readily lending itself for automatic and continuous operation.

A primary object of the present invention is the provision of a sheet stacking apparatus wherein each sheet is stacked in an inclined manner with a portion of the upper surface thereof in coextensive contact with a corresponding portion of the undersurface of the preceding sheet.

Another object of the present invention is the provision of a new and improved sheet stacking apparatus including an inclined support table having lifting means engageable with the underside of the trailing portion of each sheet thereby to lift such trailing portion for receiving successive sheets thereunder.

Still another object of the present invention is the provision of a sheet stacking apparatus for a duplicating machine of the type described, which stacking apparatus includes means engageable with the leading portion of each master sheet for temporarily holding the latter adjacent the entrance of the duplicating unit and lifting means engageable with the trailing portion of each master sheet for lifting such trailing portion above the leading portion of the sheet.

Another object of the present invention is the provision of a stacking apparatus for a duplicating machine of the type described, wherein such stacking apparatus includes sensing devices for the continuous and automatic operation of the duplicating machine.

These and other objects and advantages of the present invention will become apparent from the following specification disclosing a preferred embodiment shown in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a duplicating machine in which the present invention is embodied;

FIG. 2 is a perspective view of the stacking apparatus of the present invention;

FIG. 3 is an enlarged side view of the stacking apparatus;

FIG. 4 is an enlarged top view taken along the line 4-4 of FIG. 3;

FIG. 5 is a front view taken along the line 55 of FIG. 3;

FIG. 6 is a section taken along the line 6-6 of FIG. 5;

FIG. 7 is a partial section taken along the line 7-7 of FIG. 3;

FIG. 8 is an enlarged side elevation, diagrammatic in form, primarily illustrating the parts for feeding each sheet from the stacking apparatus to the duplicating I unit; and

FIG. 9 is an electrical schematic showing the electrical components of the stacking apparatus and the duplicating unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT A duplicating machine in which the present invention is incorporated is illustrated in FIG. 1. This machine includes an electrostatic copying unit, generally designated 10, which unit may be the Model 675 Electrostatic Copier manufactured by the assignee of this application. As is known to those skilled in the art, such a copier includes a support or platen 11 for receiving a sheet of original material thereby to make one or more electrostatic copies thereof. This copier includes a control console 12 mounting the various controls, such as an on-off button 14, an auto/start button 15, an etch button 16, a print button 17, a stop button 18, a sort button 19, a toner'indicator light 20, a re-load indicator light 21, an exposure dial 22 and a quantity selector and counter mechanism 23. This electrostatic copier is associated with a conversion unit or etcher, generally designated 25. This etcher may be the Model 167 Conversion Unit also manufactured by the assignee of this application.

It will be understood that the electrostatic copying unit is adapted to make an electrostatic copy of a sheet of original material. The conversion unit 25 converts the surface coating in the background areas of the electrostatic copy to hydrophilic condition so that the sheet may serve as a lithographic master.

The duplicating machine includes a duplicating unit, generally designated 26. This unit may be the Model 369A Offset Duplicator manufactUred by the assignee of this application. The duplicating unit receives the masters one at a time and makes duplicates in accordance with the well known offset process of imaging a blanket that then contacts the receiving sheets which are supported in a stack. The master sheet is affixed to a master cylinder which is associated with an offset cylinder and an impression cylinder and makes duplicates of the master sheet in a manner known in the art. For a description of such duplicating unit, reference may be had to Tonkin et al US. Pat. No. 3,603,253, assigned to the assignee of the present application.

The electrostatic copying unit 10 and the conversion unit 25 are capable of making successive masters rapidly. By way of example, the aforementioned Model 675 Electrostatic Copier and the Model 167 Conversion Unit are capable of making to master sheets per minute. The time required for the duplicating unit 26 to make the first copy is approximately a minute; the time required for the duplicating unit to make the desired number of copies is of course usually substantially longer. The stacking apparatus of the present invention, generally designated 28, is mounted between the outlet ofthe conversion unit 25 and the inlet of the duplicating unit 26 and provides for the stacking and temporary storing of the master sheets and for the automatic feeding of the master sheets successively to the duplicating unit at times when the latter is ready to receive the next master sheet.

Referring now particularly to FIGS. 2 through 7, the stacking apparatus will be seen to include a pair of parallel, horizontally spaced apart support bars 30 suitably supported by the housing of the duplicating unit and mounted at the opposite end of the conversion unit. The support bars rotatably mount a shaft 31 on which is mounted a roller 32 having annular surfaces 32a. The bars 30 also rotatably mount a shaft 33 above the shaft 31 in parallel relation with the latter. The shaft 33 mounts a plurality of rollers 34 for respective rolling engagement with the annular collar surface 32a.

As noted in FIG. 7, the shaft 31 includes an extension 31a mounting a sprocket wheel 36 engaged a drive chain 37. This drive chain is driven by a sprocket (not shown) forming part of the conversion unit 25. As noted in FIG. 3, the conversion unit includes a pair of rollers 39 which feeds each lithographic master to an arcuate guide 40 of suitable construction, which guide directs the master sheet to the nips of the rollers 32a, 34.

The support bars 30 rotatably mount a shaft 42 in parallel, horizontally spaced relationship with the shaft 31. The shaft 42 mounts a roller 43 having annular surfaces 43a adjacent its respective opposite ends and additional annular surfaces 43b spaced along the length of the roller. This roller also includes at its midpoint another annular formation 430.

A plurality of belts 45 are trained around the rollers 32 and 43; these belts and the rollers 32, 43 in essence constitute a horizontally disposed conveyor for advancing each master sheet from right to left, as seen in FIG. 3. Preferably, a pair of horizontally disposed side guide rails 460 are mounted adjacent the belts 45 in parallel relationship therewith to aid in guiding the master sheets during their horizontal path of travel through the stacking apparatus. It may also be desirable to provide a hold-down bail 46b to prevent the master sheets from curling down such portion of their path of travel.

A sensor switch 48 is suitably mounted in the stacking apparatus in proximity to the exit end or left side of the stacking apparatus, as noted in FIGS. 3 and 4. This switch includes a sensing arm 49 which is depressed or actuated upon being engaged by the undersurface of a passing master sheet thereby to close contacts 48a (FIG. 9). The purpose of the sensor switch 48 will be explained hereinbelow.

Another shaft 52 is suitably joumaled by the bars 30 in parallel and vertically spaced relation with the shaft 42. The shaft 52 mounts end rollers 53 in frictional engagement with the annular surfaces 43a of the roller 43 thereby to provide driving of the rollers 53 in response to rotation of the roller 43. As explained above, the roller 43 is rotated by reason of its engagement with the belts 45. Another pair of rollers 54 is mounted on the shaft 52 in alignment and in closely spaced relation with the annular surfaces 43b of the roller 43. A roller 55 is mounted on the shaft 52 in alignment with the roller surface 430 and in closely spaced relation with the latter.

The stacking apparatus includes a support plate 57 having the side marginal portions thereof bent to form flanges 58. A bracket 59 is secured to each of the flanges 58; these brackets are apertured and are rotatably received on the shaft 52 thereby constituting a pivotal mounting for the support plate 57. In other words, the plate 57 may be pivoted or swung about an axis defined by the shaft 52. Correspondind ends of arms 60 are pivotally engaged with the flanges 58 intermediate the ends of the latter. The other ends of the arms 60 include slots 60a receiving fasteners 61, the latter being mounted on the bars 30. Fasteners 61 and slots 60a permit adjustment of the angle of inclination of the support plate 57; according to a preferred embodiment of the invention, the plate 57 is disposed at an angle, with respect to the horizontal, of approximately 60.

The support plate 57 includes a rectangular depression 62; a pair of ears 63 project outwardly adjacent the sides of this depression and are apertured for rotatably supporting a shaft 64. This shaft mounts a pair of rollers 65 adjacent its respective opposite ends as well as a central roller 66.

A recess 67 is formed in the plate 57 along the lower marginal portion thereof. A pair of ears (not shown) integral with the plate 57 extend from the ends of the recess 67 and rotatably mount a shaft 68. This shaft mounts at its respective ends a pair of rollers 69. A roller is mounted on the shaft 68 at the midpoint of the latter.

Each set of rollers 54, 65 supports a belt 72; these belts are engaged by the rollers 69 as best seen in FIG.

2. The rollers 55, 68 support a belt '73; this belt is engaged by the roller 70 also as seen in FIGS. 2 and 5.

From FIG. 5 is it noted that the belts 72 are engaged by the annular roller surface 43b as the belts pass around the rollers 54. The belts 72 may be driven by this engagement with the rollers 43b and/or their engagement with the rollers 54. Similarly, the belt 73 is driven by theannular roller formation 43c and/or from the engagement of this belt with the roller 55.

As will be explained hereinbelow, the belts 72, 73 engage the trailing portion of a master sheet and lift such trailing portion such that it rests against the belts and the upper portion of the plate 57, depending on the length and number of sheets. Successive master sheets are lifted in the same manner with a substantial portion of the upper surface of each master in coextensive contact with a corresponding portion of the underside of the preceding master. In some instances, a substantial number of master sheets are so stacked and held by the plate 57. It is desirable to support the stacked sheets adjacent their side edges to prevent the sheets from becoming misaligned during the stacking operation and during the subsequent one-at-a-time feeding of the master sheets to the duplicating unit.

A support for the side edges of the stacked master sheets is provided by a pair of angle members 75, each having flanges 76 and 77, the flanges 76 being adapted to engage the side edges of the master sheets. The flanges 77 are connected to respective brackets 78. Each bracket has the ends thereof bent to form ears 79; these cars are apertured for slidably mounting the brackets 78 on a rod 80. The rod 80 is mounted from the support plate 57 by having its opposite ends received within apertures formed in the flanges 58. A bow spring 81 is secured at its central portion to each bracket 78, the ends of such spring being urged against the rod 80 thereby to hold the bracket 78, and consequently the associated angle 75, in any selected position. The support plate 57 includes a transversely extending slot 83 to accommodate sliding movement of the brackets 79 along the rod 80.

An extension plate 85 is slidably mounted adjacent the rear surface of the support plate 57. The extension plate is mounted for adjustable sliding movement longitudinally of the plate 57 and to this end includes a slot 86 receiving a fastener 87. The extension plate 85 is used to support the trailing portions of master sheets having a length somewhat greater than the length of the support plate 57.

The support bars mount a lower guide plate 88, as by means of fasteners 89. This guide plate has a horizontally disposed portion 88a in substantial coplanar relation with the upper runs of the belts 45; this guide plate has downwardly inclined portion 88b, the free end of which is disposed over an inclined plate 90 forming part of the duplicating unit 26. The guide plate 88 supports another guide plate 92 by means of a pair of fasteners 93 each including a spacer 93a. The guide 92 includes a portion 92a which, by reason of the spacers 93a, is in parallel spaced relationship with the guide plate portion 88b thereby to form a slot constituting the exit or outlet of the stacking apparatus. The guide plate 92 includes another portion 92b for guiding the leading portion of each master sheet to the outlet of the stacking apparatus.

Referring to FIG. 8, the duplicating unit 26 includes a master feed roller 95 engageable with the upper surface of each master sheet for feeding or advancing the same. The roller 95 is mounted in parallel spaced relationship with a stationary roller 96. The adjacent peripheral surfaces of the rollers 95, 96 define a space or metering slot having a thickness substantially the same as the thickness of each master sheet thereby to permit one-at-a-time movement of the master sheets through the slot defined by these two rollers. The guide plate directs the master sheet to the space between the rollers 95, 96.

The duplicating unit also includes a pair of forwarding rollers 99, 1100. Roller 99 is mounted for up and down swinging movement; roller 100 is rotatably mounted in a fixed position. Roller 99 is swung toward roller 100 sequentially to squeeze a master between the rotating rollers. It will be understood the rollers 99, 100 forward each master to a master cylinder 1011; the master sheet is wrapped around this cylinder and held in place by a clamp 102.

As each master sheet passes through the space defined by the rollers 99, 100, it engages and depresses a feeler arm 104, which feeler controls switches 104a and 1104b (FIG.,9). After the master sheet passes the feeler 104, the leading edge of such master comes into abutting engagement with a movable stop 105. Reference should be made to the aforementioned Tonkin et al patent for a detailed description of the operation of the stop 1105 and the associated components within the duplicating machine.

Referring now to the electrical schematic of FIG. 9, the master feed roller is driven by an electric motor 106. At this time it should be mentioned that the switch 48a is normally open, whereas the switch 104a is normally closed. The switch 10412 is normally open and is connected to a control circuit 109 of the duplicating unit 26.

The operation of the duplicating machine in which the present invention is incorporated is as follows:

Electrical power is applied to the electrostatic copying unit 110, the conversion unit 25 and the duplicating unit 26. This application of power will cause the chain 37 to be driven thereby in turn driving the various rollers and belts of the stacking apparatus 28. As soon as the first master sheet is formed, the same will be carried by the belts 45 until the master sheet engages and depresses the feeler 49 thereby closing the switch 48a and energizing the motor 106. The motor 106 will drive the master feed roller 95 in a clockwise direction, as seen in FIG. 8. The master feed roller will engage the upper surface of the first master sheet and feed the same to the forwarding rollers 99, 100, which rollers will advance the master until the leading edge thereof abuts the stop 1105. Just prior to reaching the stop 105, the master will engage and depress the feeler 104 thereby opening the switch 104a and de-energizing the motor 106. Accordingly, the master feed roller 95 will no longer be driven, but will be in a free wheeling condition to allow passage of the master sheet by the driving engagement of the forwarding rollers 99, 100.

Actuation of the feeler 104 causes closing of the switch lltl lthereby to apply power to the control circuit 1109 of the duplicating unit. This results in movement of the stop 105 away from the leading edge of the master thereby to allow the rollers 99, to forward the master sheet to the master cylinder 101 thereby to commence a duplicating cycle.

Assume that the duplicating unit 26 in in the process of making duplicate sheets from a master on the cylinder 101 at the time a second master exits from the conversion unit 25. The second master will engage the feeler 49 thereby to close the switch 48a; the master feed roller 95 is then driven by the motor 106 through the normally closed switch 104a. The second master sheet is advanced until the leading edge thereof comes into engagement with the stop 105. Just prior to reaching the stop 105, the second master will engage and depress the feeler 104 for opening of the switch 104a thereby to de'energize the motor 106. The second master will then be in position with the leading edge thereof abutting the stop 105 and ready for application to the cylinder 101 upon completion of the first duplicating cycle. The trailing portion of the second master sheet is engaged by the belts 72, 73 as such portion passes the rollers 43, 53, 54 and 55. These belts will lift the trailing portion and support the latter in an inclined position with the master sheet resting against the upwardly traveling belts.

Now assume that a third master is fed to the stacking apparatus at such time as the first master sheet is still on the master cylinder 101. The leading portion of the third master is fed under the lifted trailing portion of the second master sheet; the leading portion of the third master will be arrested or stopped as it approaches the space between the master feed rollers 95 and 96, as such space will still be occupied by the second master sheet. As the trailing portion of the third master sheet passes through the rollers 43, 53, 54 and 55, the belts 72, 73 will lift such trailing portion and stack the third master under the second master.

In FIG. 3, the second master sheet is designated 110 and the third master sheet is designated 111. The third master sheet will be stacked in inclined relation with a substantial area of the upper surface of the latter in coextensive contact with a corresponding portion of the undersurface of the second master 110. it will be understood that a number of successive masters will be stacked by the stacking apparatus 28 with the trailing portion of each sheet elevated above its leading portion and with each sheet stacked against the preceding sheet with a substantial portion of the upper surface of the former in coextensive engagement with a corresponding portion of the underside of the latter.

Assume that a number of masters has been stacked by the stacking apparatus as just explained and that a duplicating cycle has just been completed whereupon the first master will be ejected from the cylinder 101. The stop 105 will be automatically moved away from the leading edge of the second master sheet 110 and the same will be fed to the master cylinder by means of the forwarding rollers 99, 100. As the second master sheet passes the feeler 104, the same will be allowed to raise thereby closing the switch 104a. The motor 106 is now energized independently of the switch 48a, as by means of a switch 112 operated by the control circuit 109. The third master sheet will be driven by the master feed roller 95 until the leading edge thereof comes to rest against the stop 105. As such master passes the feeler 104, the switch 104a will again be opened deenergizing the motor 106. It will be understood that the successive stacked master sheets will be automatically fed to the cylinder 101 at the completion of each duplicating cycle. Preferably, the control circuit 109 will deenergize one or more of the units of the duplicating machine when the last master sheet is ejected from the cylinder 101, i.e., when a master sheet is not in position against the stop for being fed to the master cylinder.

We claim:

1. In a sheet handling mechanism which includes first sheet feeding means and second sheet feeding means arranged to receive sheets one at a time from the first sheet feeding means, wherein the sheets are fed through said first sheet feeding means at a rate greater than the rate they are fed through said second sheet feeding means, a stacking apparatus comprising, arresting means adjacent the entrance of said second sheet feeding means and adapted to engage the leading portion of a first sheet thereby temporarily to arrest movement of said first sheet, elevating means adjacent the outlet of said first sheet feeding means and engageable with the underside of said first sheet for elevating the trailing portion thereof above the leading portion thereof, said elevating means acting continuously against the underside of said first sheet thereby to maintain the trailing portion thereof above the leading portion thereof at all times that the leading portion of said first sheet is engaged with said arresting means, guide means for directing the leading portion of a second successive sheet to a position adjacent the underside of said first sheet, said elevating means being adapted to engage the underside of said second sheet for elevating the trailing portion thereof above the leading portion thereof in the same manner as said first sheet and thereby to stack said second sheet against said first sheet with at least a portion of the upper surface of the former in coextensive engagement with a corresponding portion of the lower surface of the latter, said guide means and said elevating means cooperating to stack each successive sheet with its trailing portion elevated above its leading portion and with at least a portion of the upper surface of each successive sheet in coextensive engagement with a corresponding portion of the lower surface of the preceding sheet.

2. The stacking apparatus according to claim 1 wherein said elevating means comprises, planar support means extending generally transversely of the path of sheet travel and mounted in an inclined position with the lower portion of said support means adjacent the outlet of said first sheet feeding means and with the upper portion of said support means disposed upstream with respect to said lower portion, an elevating element adjacent said support means and adapted for frictional engagement with the underside of each of said sheets, powered means for moving said element along a path, a portion of which path extends in an upward direction generally parallel with said support means.

3. The stacking apparatus according to claim 2 further defined by, said elevating element being constituted by a belt, upper and lower rollers supporting said belt, said powered means including drive means connected to at least one of said rollers.

4. In a sheet handling mechanism which includes first sheet feeding means and a second sheet feeding means arranged to receive sheets one at a time from the first sheet feeding means, wherein the sheets are fed through said first sheet feeding means at a rate greater than the rate they are fed through said second sheet feeding means, a stacking apparatus mounted between said first and second sheet feeding means and comprising:

a. arresting means adjacent the entrance of said second sheet feeding means and adapted to engage the leading portion of a first sheet thereby temporarily to arrest movement of said first sheet, said arresting means including a roller;

b. drive means for said roller;

c. gauge means defining, with the periphery of said roller, a slot for feeding said sheets one at a time to said second sheet feeding means in response to rotation of said roller;

d. first sensing means operable in response to the presence of said leading portion of said first sheet at said arresting means to deactuate said drive means;

e. elevating means adjacent the outlet of said first sheet feeding means and engageable with the underside of said first sheet for elevating the trailing portion thereof;

f. guide means for directing the leading edge portion of said second successive sheet to a position adjacent the underside of said first sheet;

g. said elevating means being adapted to engage the underside of said second sheet for elevating the trailing portion thereof above the leading portion thereof and thereby to stack said second sheet against said first sheet with at least a portion of the upper surface of the former in coextensive engagement with a corresponding portion of the lower surface of the latter, said guide means and said elevating means cooperating to stack each successive sheet with its trailing portion elevated above its leading portion and with at least a portion of the upper surface of each successive sheet in coextensive engagement with a corresponding portion of the lower surface of the preceding sheet;

h. second sensing means upstream of said first sensing means and operable in response to the passage of each sheet thereby to generate a signal for the activation of said drive means.

5. The stacking apparatus according to claim 4 wherein said elevating means comprises, planar support means extending generally transversely of the path of sheet travel and mounted in an inclined position with the lower portion of said support means adjacent the outlet of said first sheet feeding means and with the upper portion of said support means disposed upstream with respect to said lower portion, an elevating element adjacent said support means and adapted for frictional engagement with the underside of each of said sheets, powered means for moving said element along a path, a portion of which path extends in an upward direction generally parallel with said support means.

6. The stacking apparatus according to claim 5 further defined by, said elevating element being constituted by a belt, upper and lower rollers supporting said belt, said powered means including drive means connected to at least one of said rollers.

7. The stacking apparatus according to claim 4 further defined by:

a. said drive means including an electric motor;

b. said first and second sensing means including respective first and second switches; and

c. a control circuit connected with said electric motor and said first and second switches, said control circuit acting normally to energize said electric motor when said second sensing means detects passage of a sheet and to deenergize said electric motor when said first sensing means detects the presence of a sheet.

8. In a machine of the type including a first section for making an electrostatic copy from a sheet of original material, a second section for converting said copy to a master sheet, and a third section for making duplicates of said master sheet by direct contact between the latter and receiving sheets, wherein said first and second sections are capable of making a first master sheet and successively one or more additional master sheets in a period of time less than the time required for said third section to make a selected number of duplicates of said first master sheet, a sheet stacking apparatus mounted between said second and third sections and comprising:

a. first means engageable with the leading portion of an additional master sheet for temporarily holding the latter adjacent the entrance of said third section at times when the latter is making duplicates from said first master;

b. second means including elevating means engageable with the trailing portion of said additional master for lifting said trailing portion above said leading portion said elevating means acting continuously against the underside of said additional master thereby to maintain the trailing portion thereof above the leading portion thereof at all times that the leading portion of said additional master is engaged with said first means; and

c. said first and second means cooperating to stack each successive additional master against the immediately preceding master with a portion of the upper surface of each of said additional masters in coextensive contact with a corresponding portion of the lower surface of the immediately preceding master.

9. The sheet stacking apparatus according to claim 8 further defined by:

a' said first means including a roller and drive means therefor, which roller is arranged to engage said first additional master sheet for feeding the same to the entrance of said third section;

b. first sensing means operable in response to the presence of the, leading edge portion of said first additional master sheet at an entrance of said third section;

c. second sensing means operable in response to the passage of an additional master sheet at a location upstream from said first sensing means; and

d. control means connected with said first and second sensing means for actuating said drive means upon operation of said second sensing means and for deactuating said drive means upon operation of said first sensing means.

10. The stacking apparatus according to claim 8 wherein said elevating means comprises, planar support means extending generally transversely of the path of sheet travel and mounted in an inclined position with the lower portion of said support means adjacent the outlet of said first sheet feeding means and with the upPer portion of said support means disposed upstream with respect to said lower portion, an elevating element adjacent said support means and adapted for frictional engagement with the underside of each of said sheets, powered means for moving said element along a path, a portion of which path extends in an upward direction generally parallel with said support means. 

1. In a sheet handling mechanism which includes first sheet feeding means and second sheet feeding means arranged to receive sheets one at a time from the first sheet feeding means, wherein the sheets are fed through said first sheet feeding means at a rate greater than the rate they are fed through said second sheet feeding means, a stacking apparatus comprising, arresting means adjacent the entrance of said second sheet feeding means and adapted to engage the leading portion of a first sheet thereby temporarily to arrest movement of said first sheet, elevating means adjacent the outlet of said first sheet feeding means and engageable with the underside of said first sheet for elevating the trailing portion thereof above the leading portion thereof, said elevating means acting continuously against the underside of said first sheet thereby to maintain the trailing portion thereof above the leading portion thereof at all times that the leading portion of said first sheet is engaged with said arresting means, guide means for directing the leading portion of a second successive sheet to a position adjacent the underside of said first sheet, said elevating means being adapted to engage the underside of said second sheet for elevating the trailing portion thereof above the leading portion thereof in the same manner as said first sheet and thereby to stack said second sheet against said first sheet with at least a portion of the upper surface of the former in coextensive engagement with a corresponding portion of the lower surface of the latter, said guide means and said elevating means cooperating to stack each successive sheet with its trailing portion elevated above its leading portion and with at least a portion of the upper surface of each successive sheet in coextensive engagement with a corresponding portion of the lower surface of the preceding sheet.
 2. The stacking apparatus according to claim 1 wherein said elevating means comprises, planar support means extending generally transversely of the path of sheet travel and mounted in an inclined position with the lower portion of said support means adjacent the outlet of said first sheet feeding means and with the upper portion of said support means disposed upstream with respect to said lower portion, an elevating element adjacent said support means and adapted for frictional engagement with the underside of eAch of said sheets, powered means for moving said element along a path, a portion of which path extends in an upward direction generally parallel with said support means.
 3. The stacking apparatus according to claim 2 further defined by, said elevating element being constituted by a belt, upper and lower rollers supporting said belt, said powered means including drive means connected to at least one of said rollers.
 4. In a sheet handling mechanism which includes first sheet feeding means and a second sheet feeding means arranged to receive sheets one at a time from the first sheet feeding means, wherein the sheets are fed through said first sheet feeding means at a rate greater than the rate they are fed through said second sheet feeding means, a stacking apparatus mounted between said first and second sheet feeding means and comprising: a. arresting means adjacent the entrance of said second sheet feeding means and adapted to engage the leading portion of a first sheet thereby temporarily to arrest movement of said first sheet, said arresting means including a roller; b. drive means for said roller; c. gauge means defining, with the periphery of said roller, a slot for feeding said sheets one at a time to said second sheet feeding means in response to rotation of said roller; d. first sensing means operable in response to the presence of said leading portion of said first sheet at said arresting means to deactuate said drive means; e. elevating means adjacent the outlet of said first sheet feeding means and engageable with the underside of said first sheet for elevating the trailing portion thereof; f. guide means for directing the leading edge portion of said second successive sheet to a position adjacent the underside of said first sheet; g. said elevating means being adapted to engage the underside of said second sheet for elevating the trailing portion thereof above the leading portion thereof and thereby to stack said second sheet against said first sheet with at least a portion of the upper surface of the former in coextensive engagement with a corresponding portion of the lower surface of the latter, said guide means and said elevating means cooperating to stack each successive sheet with its trailing portion elevated above its leading portion and with at least a portion of the upper surface of each successive sheet in coextensive engagement with a corresponding portion of the lower surface of the preceding sheet; h. second sensing means upstream of said first sensing means and operable in response to the passage of each sheet thereby to generate a signal for the activation of said drive means.
 5. The stacking apparatus according to claim 4 wherein said elevating means comprises, planar support means extending generally transversely of the path of sheet travel and mounted in an inclined position with the lower portion of said support means adjacent the outlet of said first sheet feeding means and with the upper portion of said support means disposed upstream with respect to said lower portion, an elevating element adjacent said support means and adapted for frictional engagement with the underside of each of said sheets, powered means for moving said element along a path, a portion of which path extends in an upward direction generally parallel with said support means.
 6. The stacking apparatus according to claim 5 further defined by, said elevating element being constituted by a belt, upper and lower rollers supporting said belt, said powered means including drive means connected to at least one of said rollers.
 7. The stacking apparatus according to claim 4 further defined by: a. said drive means including an electric motor; b. said first and second sensing means including respective first and second switches; and c. a control circuit connected with said electric motor and said first and second switches, said control circuit acting normally to energize said electric motor when said second sensing means detects passage of a sheet and to deenergize said electric motor when said first sensing means detects the presence of a sheet.
 8. In a machine of the type including a first section for making an electrostatic copy from a sheet of original material, a second section for converting said copy to a master sheet, and a third section for making duplicates of said master sheet by direct contact between the latter and receiving sheets, wherein said first and second sections are capable of making a first master sheet and successively one or more additional master sheets in a period of time less than the time required for said third section to make a selected number of duplicates of said first master sheet, a sheet stacking apparatus mounted between said second and third sections and comprising: a. first means engageable with the leading portion of an additional master sheet for temporarily holding the latter adjacent the entrance of said third section at times when the latter is making duplicates from said first master; b. second means including elevating means engageable with the trailing portion of said additional master for lifting said trailing portion above said leading portion said elevating means acting continuously against the underside of said additional master thereby to maintain the trailing portion thereof above the leading portion thereof at all times that the leading portion of said additional master is engaged with said first means; and c. said first and second means cooperating to stack each successive additional master against the immediately preceding master with a portion of the upper surface of each of said additional masters in coextensive contact with a corresponding portion of the lower surface of the immediately preceding master.
 9. The sheet stacking apparatus according to claim 8 further defined by: a. said first means including a roller and drive means therefor, which roller is arranged to engage said first additional master sheet for feeding the same to the entrance of said third section; b. first sensing means operable in response to the presence of the leading edge portion of said first additional master sheet at said entrance of said third section; c. second sensing means operable in response to the passage of an additional master sheet at a location upstream from said first sensing means; and d. control means connected with said first and second sensing means for actuating said drive means upon operation of said second sensing means and for deactuating said drive means upon operation of said first sensing means.
 10. The stacking apparatus according to claim 8 wherein said elevating means comprises, planar support means extending generally transversely of the path of sheet travel and mounted in an inclined position with the lower portion of said support means adjacent the outlet of said first sheet feeding means and with the upPer portion of said support means disposed upstream with respect to said lower portion, an elevating element adjacent said support means and adapted for frictional engagement with the underside of each of said sheets, powered means for moving said element along a path, a portion of which path extends in an upward direction generally parallel with said support means. 